Microsoft Corp is getting ready to unveil a long-anticipated free anti-virus service for personal computers that will compete with products sold by Symantec Corp and McAfee Inc.

Investors are closely monitoring the free service, code-named Morro after Brazil's Morro de Sao Paolo beach, amid concern it could hurt sales of products from Symantec and McAfee, which generate billions of dollars of revenue a year protecting Windows PCs from attacks by hackers.

Three years ago, Microsoft entered that market with Live OneCare, which turned out to be a commercial flop. It announced plans in November to kill that product suite, saying it would launch the free Morro service by the end of 2009.

Analysts said they are looking forward to Morro's beta to see exactly how its features compare to those in products from competitors.

Microsoft has said it will provide protection from several types of malicious software including viruses, spyware, rootkits and trojans.

Officials with Symantec and McAfee have said they do not see Morro as a threat.

"Microsoft's free product is basically a stripped down version of the OneCare product Microsoft pulled from the shelves," said Symantec Consumer division president Janice Chaffin. "A full Internet security suite is what consumers require today to stay fully protected."

Joris Evers, a spokesman for No. 2 security software maker McAfee, said his company is already enjoying strong growth despite competition from free anti-virus products that are on the market.

"On a level playing field, we are confident in our ability to compete with anyone who might enter the marketplace," he said.

A spokeswoman for Trend Micro Inc, the No. 3 player, declined to comment.